The Pleiades cluster logo used by Subaru is a tribute to its formation back in the years following World War II. This group of six stars (some say seven or nine, but only the six are most visible) is represented by a large star, Alcyone. In Subaru's case, it refers to Fuji Heavy Industries (FHI), its parent company. The other stars refer to the small firms that united to give birth to FHI.
FHI started out as the Aircraft Research Laboratory, established in 1917 by Chikuhei Nakajima and renamed as the Nakajima Aircraft Factory a year later. It was in the business of producing carrier and land-based aircraft for the military, some of which like the Ki-43 Hayabusa and Ki-84 Hayate ("Oscar" and "Gale" to the Allies) saw action during the war.
The company reorganized itself after Japan's surrender in August 15, 1945 as Fuji Sangyo Co., Ltd. and entered into a different business: making scooters. The company would go on to make the first Subaru—the 1.5-liter, 45-hp P-1—in 1954. In 1955, Fuji Sangyo acquired the following smaller companies:
Fuji Kogyo, scooter manufacturer
Fuji Jidosha Kogyo, bus body manufacturer
Omiya Fuji Kogyo, engine manufacturer
Utsunomiya Sharyo, vehicle chassis manufacturer
Tokyo Fuji Sangyo, trading company
Interestingly, the word "subaru" means "unite." Since then, many Japanese have associated the name with the Pleiades cluster. FHI maintains an aeronautics division, but its important assets are with the automotive industry.